Difference of the recurrence graph slope for independent earthquakes and aftershock sequences

Abstract

In work necessity of aftershock sequences removal from the catalogue of earthquakes at estimation of the recurrence graph slope γ -value is justified. Calculations were made at several thresholds of minimal number of used earthquakes N = 100, 50 and 25 for all earthquakes from the catalogue (γ _all), for the grouped earthquakes (namely, aftershocks) - γ _aft and for background events (γ _bckgr) in the spatial area of aftershock sequences. Z-parameter (normalized difference) and Kolmogorov-Smirnov's criterion were used for comparison of the received γ _aft-value with γ _bckgr-value (γ _all with γ _bckgr and γ _all with γ _aft) and for check of a H0-hypothesis about equality of these values. Z-distribution analysis shows statistically significant distinction of considered values. The received significance levels prove necessity of aftershock sequences removal from the catalogue of earthquakes at calculation of γ -value as parameter of seismicity.